1. Field of the Invention
The present invention relates to a hand-held drive-in tool for driving fastening elements in a workpiece and including a guide, a displaceable drive-in ram for driving the fastening elements in the workpiece, at least one drive spring member for driving the drive-in ram, a preloading device for the drive-in ram and the drive spring member, a locking device having a locking position in which the locking device retains the drive-in ram and the drive spring member in a preloaded position, and an actuation switch imitating a drive-in process and for displacing the locking device in a release position thereof.
2. Description of the Prior Art
The drive-in tool of the type described above can be, e.g., electrically driven, with the drive spring member, which can be preloaded by an electrically driven, preloading device, serving as an energy accumulator. The advantage of such drive-in tools consists in their simple and easily produced construction.
A drive-in tool of the type described above, which is formed as an electric tacker, is disclosed in German Publication DE 32 37 087 A1. In this drive-in tool, a drive-in ram, which is formed as a firing pin, is displaced by a rotatable electric motor in a preloaded position against a biasing force of a drive spring member. The driving connection between the drive-in ram and the electric motor is so formed that he drive-in ram is decoupled from the motor in its preloaded position in which the drive-in ram is held by a locking member. To initiate a drive-in process, an actuation switch, such as an actuation lever or a pressure button should be actuated. Upon actuation of the actuation switch, the locking member is displaced from its locking position in which it retains the drive-in ram in its preloaded position, to a release position. The fastening elements, which are driven in by the electric tacker are stored in a magazine.
The drawback of the known drive-in tool consists in that when no drive-in process is actuated, e.g., when the drive-in tool after being pressed against a workpiece, is lifted off again, without the actuation of the actuation switch, the drive spring member remains preloaded, that can lead to spring fatigue.
Drive-in tools such as described above, electric tacker, have, as a rule, a very small drive-in energy of about from 5 to 10J. Should there be provided such drive-in tool with a greater drive-in energy of up to 80J, a corresponding adaptation or scaling of the drive spring member becomes necessary, which significantly increases the danger of fatigue if the drive spring member remains in preloaded condition for a long period of time.
Accordingly, an object of the present invention is to provide a drive-in tool of the type described above in which the above-discussed drawback of a known tool is eliminated.